is it dual channel?
i had many weird problems with dual channel memory
they have to be the EXACT SAME STICK....or you will most likely get errors
even if it isnt dual channel id reccomend trying.....
my friend also had a problem with using registered ecc ddr ram....
lastly check to see if anything is shorted on the board.... extra screw spacers, screw that fell in the case while installing.... that can cause some nasty problems aswell